Management Of Asian Citrus Psyllid Research Articles

Volatile Dimethyl Disulfide from Guava Plants Regulate Developmental Performance of Asian Citrus Psyllid through Activation of Defense Responses in Neighboring Orange Plants.

Intercropping with guava (Psidium guajava L.) can assist with the management of Asian citrus psyllid (ACP, Diaphorina citri Kuwayama), the insect vector of the huanglongbing pathogen, in citrus orchards. Sulfur volatiles have a repellent activity and physiological effects, as well as being important components of guava volatiles. In this study, we tested whether the sulfur volatiles emitted by guava plants play a role in plant–plant communications and trigger anti-herbivore activities against ACP in sweet orange plants (Citrus sinensis L. Osbeck). Real-time determination using a proton-transfer-reaction mass spectrometer (PTR-MS) showed that guava plants continuously release methanethiol, dimethyl sulfide (DMS), and dimethyl disulfide (DMDS), and the contents increased rapidly after mechanical damage. The exposure of orange plants to DMDS resulted in the suppression of the developmental performance of ACP. The differential elevation of salicylic acid (SA) levels; the expression of phenylalanine ammonia lyase (PAL), salicylate-O-methyl transferase (SMT), and pathogenesis-related (PR1) genes; the activities of defense-related enzymes PAL, polyphenol oxidase (PPO), and peroxidase (POD); and the total polyphenol content were observed in DMDS-exposed orange plants. The emission of volatiles including myrcene, nonanal, decanal, and methyl salicylate (MeSA) was increased. In addition, phenylpropanoid and flavonoid biosynthesis, and aromatic amino acid (such as phenylalanine, tyrosine, and tryptophan) metabolic pathways were induced. Altogether, our results indicated that DMDS from guava plants can activate defense responses in eavesdropping orange plants and boost their herbivore resistance to ACP, which suggests the possibility of using DMDS as a novel approach for the management of ACP in citrus orchards.

Abundance and diversity of lacewings in grower operated organic and conventional pest management programs for Diaphorina citri (Hemiptera: Liviidae)

The lacewings (Neuroptera: Chrysopidae) are predators of several economically important pests in agriculture and they are naturally present in the citrus orchards in Brazil. However, their abundance and diversity needed to be determined in order to identify their role in the management of Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), which is an economically important pest and vector of huanglongbing. Our goals were to identify lacewing species and their abundance in the organic and conventional management programs against ACP in the citrus crops and determine the biological parameters of the predominant species on ACP. The lacewings were monitored in three municipalities of São Paulo state, Brazil, from November 2015 to June 2017. We identified Ceraeochrysa cincta (Schneider), Ceraeochrysa cubana (Hagen), Ceraeochrysa paraguaria (Navás), Chrysoperla externa (Hagen), and Chrysoperla defreitasi Brooks species and those were equally abundant between conventional and organic management psyllid management programs. Ceraeochrysa cincta was predominant in both systems, representing more than 60% of all the specimens. They developed and reproduced successfully on the diet of D. citri nymphs when compared against Ephestia kuehniella Zeller (Lepidoptera: Pyralidae) eggs. The abundance of these multiple species and predominance and development of C. cincta on D. citri suggest their potential use for biological control of D. citri in organic and conventional psyllid management programs.

Effects of the entomopathogenic fungus Clonostachys rosea on mortality rates and gene expression profiles in Diaphorina citri adults

Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a serious pest of citrus. The insect also transmits Candidatus Liberibacter asiaticus, the pathogen of a devastating citrus disease called Huanglongbing. Clonostachys rosea is a versatile fungus that possesses nematicidal and insecticidal activities. The effect of C. rosea against D. citri remains unclear. Here we examined the pathogenicity of C. rosea against D. citri adults. A mortality rate of 46.67% was observed in adults treated with 1 × 108 conidia/mL spore suspension. Comparative transcriptomic analyses identified 259 differentially-expressed genes (DEGs) between controls and samples treated with fungi. Among the DEGs, 183 were up-regulated and 76 down-regulated. Genes with altered expression included those involved in immunity, apoptosis and cuticle formation. Our preliminary observation indicated that C. rosea is virulent against ACP adults and has the potential as a biological control agent for ACP management in the field.

Candidatus Liberibacter asiaticus manipulates the expression of vitellogenin, cytoskeleton, and endocytotic pathway-related genes to become circulative in its vector, Diaphorina citri (Hemiptera: Psyllidae)

The online version contains supplementary material available at 10.1007/s13205-021-02641-x.

Host plant odours and their recognition by the odourant-binding proteins of Diaphorina citri Kuwayama (Hemiptera: Psyllidae).

The Asian citrus psyllid (ACP), Diaphorina citri, is one of the major pests in citrus production because it transmits huanglongbing, a devastating disease of citrus plants. Odourant-binding proteins (OBPs) play an important role in the olfactory perception of insects. Revealing the function of DcitOBPs is beneficial to the development of new ACP management strategies. An analysis of the components of volatiles from the new shoots of six host plant species showed that β-caryophyllene was the characteristic volatile compound in flushing shoots and the most abundant volatile compound in three of the six tested ACP host plant species. The tissue expression profiles of nine known DcitOBPs were analyzed based on a transcriptome database, and DcitOBP3 and DcitOBP6 exhibited high expression in the antennae of both sexes and the ovipositor of females. The binding ability of two recombinant proteins with eight ligands was studied through competitive binding analysis; the results showed that DcitOBP6 exhibited stronger binding to β-caryophyllene. Behavioural trials indicated that sexually mature female adults of D. citri were significantly attracted to β-caryophyllene at concentrations of 0.1 μL mL-1 and 10 μL mL-1 . RNAi analysis in female D. citri showed that the reduction of DcitOBP6 transcript abundance led to a decrease in antennae EAG activity and behavioural responses to β-caryophyllene. The results demonstrate that DcitOBP6 is involved in the perception of an important host plant volatile, β-caryophyllene, in the ACP, and provide a theoretical foundation for behavioural interference in ACP management.

Ecological Aspects of the Vector-Borne Bacterial Disease, Citrus Greening (Huanglongbing): Dispersal and Host Use by Asian Citrus Psyllid, Diaphorina Citri Kuwayama.

Determining the influence of abiotic and biotic factors on pest dispersal behavior is a critical component of integrated pest management. The behavioral and physiological traits of movement of the Asian Citrus Psyllid (ACP), Diaphorina citri Kuwayama, has received significant attention. Field and laboratory experiments have explored the physiological capabilities of ACP dispersal, as well as, the abiotic and biotic drivers that initiate movement behavior. Abiotic factors such as temperature, barometric pressure, humidity, landscape, and orchard architecture, as well as, biotic factors including mating status, pathogen infection, and morphotype have been investigated in great detail. The current review focuses on dispersal of ACP with the goal of synthesizing current knowledge to suggest management tactics. Overall, vision serves as the primary modality for host finding in ACP. Current data suggest that ACP populations increase more within uniform landscapes of seedling trees, as compared to mature orchards with randomly interspersed young seedlings. The data also suggest that establishment and conservation of visual and physical barriers might be beneficial to protect orchards from ACP. Management of ACP must take into account large-area cooperation, orchard border surveillance and treatment, removal of non-crop habitat, and an understanding that immigration can occur from distances of several kilometers.

Development and evaluation of emulsifiable concentrate formulation containing Sophora alopecuroides L. extract for the novel management of Asian citrus psyllid.

Utilization of non-host plants semiochemicals to mediate insect behavior offers a promising opportunity for novel management of insect pests in field crops and fruits. Therefore, there is still a substantial opportunity for the development of natural prophylactic as an eco-friendly approach in the novel pest management programs. Sophora alopecuroides extract has been used as a natural pesticide in the control of agricultural and household pests, but the low persistence effect and rapid biodegradability limit its use on a wider scale in pest management programs. In this study, an emulsifiable concentrate formulation containing S. alopecuroides extract (SAE-EC) was developed with a simple procedure and evaluated for its ovicidal, antifeedant, and repellent effects against Diaphorina citri under laboratory and semi-field conditions. Our results indicated that SAE-EC at 15, 30, and 50mg/mL concentrations provide complete protection against psyllids for a period of 96h after application both under laboratory andsemi-field conditions, while the aqueous methanolic extract of S. alopecuroides loses its persistence 48h after application. Furthermore, the emulsifiable concentrate at 20 and 30mg/mL concentrations, only 15.97% and 31.97% of eggs were able to hatch, and at similar concentrations, 72.86% and 85.5% of honeydew secretion were reduced as compared to the control. SAE-EC at 30mg/mL concentration has not shown any phytotoxic symptoms on Murraya paniculata seedlings. Fourier transform infrared (FTIR) study revealed the presence of alkaloids in emulsifiable concentrate after 3months of its preparation placed under ambient temperature. Furthermore, the particle size and polydispersity index (PDI) of the emulsifiable concentrate were also confirmed by dynamic light scattering (DLS). Our finding indicated that emulsifiable concentrate formulation prolongs the persistence of S. alopecuroides extract and enhances its efficacy both under laboratory and semi-field conditions. It has been concluded that the emulsifiable concentrate formulation containing S. alopecuroides extract might be developed as an eco-friendly novel prophylactic against citrus psyllid.

Toxicity of Bacillus thuringiensis-Derived Pesticidal Proteins Cry1Ab and Cry1Ba against Asian Citrus Psyllid, Diaphorina citri (Hemiptera).

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera), is an important pest of citriculture. The ACP vectors a bacterium that causes huanglongbing (HLB), a devastating and incurable disease of citrus. The bacterium Bacillus thuringiensis (Bt) produces multiple toxins with activity against a diverse range of insects. In efforts to provide additional control methods for the ACP vector of HLB, we identified pesticidal proteins derived from Bt for toxicity against ACP. The trypsin proteolytic profiles of strain-derived toxins were characterized. Strain IBL-00200, one of six strains with toxins shown to have basal activity against ACP was selected for liquid chromatography-mass spectrometry (LC-MS/MS) identification of the individual Cry toxins expressed. Toxicity assays with individual toxins derived from IBL-00200 were then performed. The activated form of the Cry toxins Cry1Ab and Cry1Ba were toxic to ACP with LC50 values of approximately 120 µg/mL. Disruption of the midgut epithelium was associated with the toxicity of both the IBL-00200-derived toxin mixture, and with Cry1Ba. With further optimization of the efficacy of Cry1Ab and Cry1Ba, these toxins may have practical utility against ACP. Bt toxins with activity against ACP may provide an additional tool for management of ACP and the associated HLB disease, thereby providing a more sustainable and environmentally benign approach than repeated application of broad-spectrum insecticides.

Association Between Citrus Flushing Cycles and Asian Citrus Psyllid Demography in Huanglongbing-Free Area in Brazil.

Diaphorina citri Kuwayama (Hemiptera: Liviidae), named as Asian citrus psyllid (ACP), is the vector of the bacterium associated with huanglongbing (HLB), the most destructive citrus disease. The use of citrus flushing and ACP monitoring tools is essential for the knowledge of the occurrence pattern of cycles of both and for the improvement of the ACP management. During 3years, 20 branches from 20 trees were evaluated for vegetative flushing, ACP abundance, and occupation in tree and branches in a Brazilian citrus area free for HLB. The obtained data was investigated through spectral and co-spectral analyses. Four to 12 flush shoot cycles occurred per year, which were similar to abundance and occupation cycles of ACP, with an apparent synchronization between these variables. In general, there was a difference from 14 to 19days between flushing and ACP peaks, with an occurrence of the flushing peaks before the ACP peaks. Results will provide useful information to citrus growers and agricultural defense agencies to apply a suitable and targeted ACP management, which will avoid or delay the disease entrance into still free HLB areas. In addition, the modeling of occupation and abundance cycles of vectors as applied in this study may be useful for other pathosystems which insect vectors are associated or even in the intrusion monitoring programs.

Life Cycle and Larval Predation byCeraeochrysa valida(Banks) on Nymphs ofDiaphorina citriKuwayama

Area-wide management of Asian citrus psyllid, Diaphorina citri Kuwayama, might use predators abundant in citrus orchards, making necessary the assessment of local predatory species such as Ceraeochrysa valida (Banks). The objective of the study was to determine the life cycle of C. valida under different rearing conditions; its fecundity, survival, and longevity; and its predatory capacity on different larval instars of D. citri, both in the laboratory and greenhouse. Predators and pests were reared from insects collected in citrus orchards in the central coastal area of Veracruz, Mexico. Developmental time for C. valida eggs; larvae 1, 2, and 3; and prepupae-pupae were 5.5 ± 0.7, 6.5 ± 0.7, 5.0 ± 1.0, 7.0 ± 1.0, and 14.5 ± 0.7 days, respectively. Male and female longevities were 74.0 ± 38.9 and 78.0 ± 28.9 days. Mean daily number of eggs per female was 10.0 ± 8.4. Predation in the laboratory and greenhouse was greater on older larvae (P < 0.0001) regardless of the nymphal stages consumed. In the laboratory, C. valida consumed as many as 368 prey in 48 hours. However, consumption in a greenhouse was not as much as in the laboratory during the first 6 hours.

Risk assessment of various insecticides used for management of Asian citrus psyllid, Diaphorina citri in Florida citrus, against honey bee, Apis mellifera.

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a major pest of citrus trees worldwide. A wide variety of insecticides are used to manage D. citri populations within citrus groves in Florida. However, in areas shared by citrus growers and beekeepers the use of insecticides may increase the risks of Apis mellifera L. (Hymenoptera: Apidae) loss and contaminated honey. The objective of this research was to determine the environmental toxicity of insecticides, spanning five different modes of action used to control D. citri, to A. mellifera. The insecticides investigated were imidacloprid, fenpropathrin, dimethoate, spinetoram and diflubenzuron. In laboratory experiments, LD50 values were determined and ranged from 0.10 to 0.53 ng/μl for imidacloprid, fenpropathrin, dimethoate and spinetoram. LD50 values for diflubenzuron were >1000 ng/μl. Also, a hazard quotient was determined and ranged from 1130.43 to 10893.27 for imidacloprid, fenpropathrin, dimethoate, and spinetoram. This quotient was <0.447 for diflubenzuron. In field experiments, residual activity of fenpropathrin and dimethoate applied to citrus caused significant mortality of A. mellifera 3 and 7 days after application. Spinetoram and imidacloprid were moderately toxic to A. mellifera at the recommended rates for D. citri. Diflubenzuron was not toxic to A. mellifera in the field as compared with untreated control plots. Phenoloxidase (PO) activity of A. mellifera was higher than in untreated controls when A. mellifera were exposed to 14 days old residues. The results indicate that diflubenzuron may be safe to apply in citrus when A. mellifera are foraging, while most insecticides used for management of D. citri in citrus are likely hazardous under various exposure scenarios.

Repellency of selected Psidium guajava cultivars to the Asian citrus psyllid, Diaphorina citri

Huanglongbing (HLB) is the most devastating disease of citrus worldwide. It is caused by bacteria of the genus ‘Candidatus Liberibacter’ and transmitted by two psyllid species, the Asian citrus psyllid (ACP) Diaphorina citri, and the African citrus psyllid Trioza erytreae. Considerable research has been conducted toward developing and implementing HLB and ACP management strategies. With respect to ACP control, of interest is that reports indicate guava, Psidium guajava, can be repellent to ACP. We conducted research to further evaluate repellency of guava to ACP. In one set of experiments, guava oil from five Brazilian guava cultivars (‘J3’, ‘Pedro Sato’, ‘Século XXI’, ‘Thailand’ and ‘Paluma’) was extracted from leaves (immature and mature) by hydro-distillation in a Clevenger-type apparatus and evaluated for psyllid repellency. In a second set of experiments, repellency of guava leaves to ACP was investigated using leaves (immature and mature) from two guava cultivars in Florida, ‘Pink’ and ‘Thai White’. In each set of experiments, repellency was evaluated by releasing ACP adults into a cage with two large vials, one containing a young flush shoot (= immature leaves) of Murraya exotica (a favored host plant of the psyllid, the flush of which is highly attractive to ACP) and one with M. exotica flush and the test material of interest (guava oil, immature guava leaf or mature guava leaf). The adults were free to move throughout the cage and into the vials, and the number of psyllids in each vial was counted after 24 h. The results showed that all guava materials tested had at least some repellency to ACP. Mature leaves tended to have a greater repellent effect than immature leaves. Each of the five oils exhibited repellency. A report in the literature suggested that sulfur compounds associated with guava may be responsible for ACP repellency. Interestingly, the five guava oil extracts we studied were repellent to ACP but none contained any sulfur compounds. Identification of the constituents responsible for repellency could lead to new ACP management tactics.

Costs and benefits of frequent low-volume applications of horticultural mineral oil for management of Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Psyllidae)

The Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), vectors a pathogen that causes huanglongbing (HLB) in Florida citrus. The need to suppress ACP populations has resulted in greatly increased insecticide use in Florida. Horticultural mineral oils (HMOs), typically applied as 1–2% v/v aqueous emulsions at 937 L water ha−1, are also used for insect pest management for citrus in Florida. Low-volume applications of other insect control products can reduce costs and application time and are effective for ACP control. The efficacy of low-volume applications of HMOs for ACP has not been tested. We initiated a three-year trial in February 2011 in a commercial Valencia orange grove in Lee County, Florida to compare low-volume (18.7 L ha−1) sprays of HMO applied every two weeks to a grower standard (GS) (mixes of insecticide and HMO) and an untreated control. HMO and GS treatments significantly reduced ACP adult and nymph populations. Yields were greater for HMO-treated than untreated trees in the final study year. GS and HMO treatments reduced fruit drop in 2013. Fruit quality was generally unaffected by treatments. ACP suppression, higher yields and eventual production gains indicated that frequent, low-volume application of HMO may be a viable alternative for suppressing ACP populations.

Chemical control of the Asian citrus psyllid and of huanglongbing disease in citrus.

By 2014, huanglongbing (HLB), the most destructive disease of citrus, and its insect vector, the Asian citrus psyllid (ACP), Diaphorina citri (Kuwayama), became established in all major citrus-growing regions of the world, including the United States, with the exception of California. At present, application of insecticides is the most widely followed option for reducing ACP populations, while application of antibiotics for suppressing HLB disease/symptoms is being practiced in some citrus-growing regions. Application of insecticides during the dormant winter season, along with cultivation of HLB-free seedlings and early detection and removal of symptomatic and asymptomatic trees, has been very effective in managing ACP. Area-wide management of ACP by application of insecticides at low volume in large areas of citrus cultivation has been shown to be effective in managing HLB and reducing management costs. As insecticide resistance is a major problem in sustainable management of ACP, rotation/alternation of insecticides with different chemistries and modes of action needs to be followed. Besides control of the insect vector, use of antibiotics has temporarily suppressed the symptoms of HLB in diseased trees. Recent efforts to discover and screen existing as well as new compounds for their antibiotic and antimicrobial activities have identified some promising molecules for HLB control. There is an urgent need to find a sustainable solution to the HLB menace through chemical control of ACP populations and within HLB-infected trees through the judicious use of labeled insecticides (existing and novel chemistries) and antibiotics in area-wide management programs with due consideration to the insecticide resistance problem.

THRESHOLDS FOR VECTOR CONTROL AND COMPATIBILITY WITH BENEFICIAL FAUNA IN CITRUS WITH HIGH INCIDENCE OF HUANGLONGBING

Huanglongbing (HLB) or citrus greening disease is vectored by the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama. Vector control is considered a basic component of HLB management even in a high disease incidence scenario. Such control is mostly chemically oriented. However, overuse of insecticides would increase costs and be incompatible with biological control. Establishment of economic thresholds for psyllid control under different price scenarios would optimize returns on investment. A 3-year experiment is being conducted in a commercial orange block with high HLB incidence. Experimental design is RCB with 4 treatments and 4 replicates: (1) calendar applications, (2) insecticide applications according to a threshold of 0.2 psyllids/stem tap sample, (3) applications according to a 0.7 threshold and (4) no insecticide. Vector populations are monitored biweekly by tap sampling. Differences in vector abundance among treatments are being correlated to fruit yields. Consequences of each vector control strategy on beneficial arthropod fauna are also being evaluated, as well as potential negative impacts on biological control. After two years, a significant yield increase was observed with the calendar treatment, but so far, justification for the additional costs would require higher than actual juice prices scenarios. ACP management strategies based on nominal thresholds are so far more profitable. Negative impacts of calendar sprays on biological control of mites and leafminers have been observed.

Asian Citrus Psyllid and Huanglongbing Management in California: How Psyllid Spread Will Affect Grower Costs

The spread of Asian Citrus Psyllid (ACP) in California is beginning to reach commercial production.&nbsp; As a vector of the pathogen associated with Huanglongbing (HLB), spread of this insect puts at risk the state's billion dollar citrus industry wherever ACP establishes. Management of ACP and infected tree removal are the only known methods of limiting the spread of HLB, but these methods come with their own set of costs and risks. To reduce economic losses, ACP management options for growers are being developed before ACP and HLB spread throughout commercial citrus growing areas in California.&nbsp; This study will present an ex-ante cost comparison of current pest control practices, the IPM best practices for ACP, and the least cost ACP management program for different citrus growing areas in California.&nbsp; Partial budgeting will be used to estimate the costs under each scenario. Partial budgeting compares the changes in income and expenses that would result from implementing a specific alternative; hence it provides an indicator as to how the treatment is likely to affect the profitability of an enterprise (Kay et al. 2004).&nbsp; Because ACP treatments are applied to reduce the risk of HLB infection and ACP causes far less significant direct damage to citrus, changes in revenues are equal to zero and only costs are calculated.&nbsp; To calculate costs, data on material and application costs were obtained from meetings with pest control advisors in California's citrus growing areas.

Brachygastra mellifica (Hymenoptera: Vespidae): Predation preference and feeding behavior on Diaphorina citri (Hemiptera: Psyllidae) in Mexico

In previous field studies in Northern Mexico, we found the wasp Brachygastra mellifica (Say 1837) (Hymenoptera: Vespidae) preying voraciously the Asian citrus psyllid (ACP), Diaphorina citri Kuwayama (Hemiptera: Psyllidae), the vector of the bacteria Ca. Liberibacter spp., the putative agent of Huanglongbing, one of the most devastating citrus disease in the world. As in Mexico, the ACP management considers the use of pest biological control, the availability of potential agents for the control of the vector remains as a priority. The objective of this study was to determine the predation preference of the wasp for the different developmental stages of D. citri. During 2011-2012, we performed experiments in field where we exposed manually to the predator new citrus flushes infested by eggs and diverse ACP nymphal instars. The predation behavior was recorded in videos and posteriorly analyzed in the lab. Other observations on its feeding attack were made directly on infested flushes in the trees, during the foraging activity of the wasp. Results indicated that B. mellifica preferred for predation 4th and 5th instar nymphs, and posteriorly 2nd and 3rd instars. Due to their size and position in the flush, eggs and first instar nymphs were practically discriminated by the wasp. Occasionally, B. mellifica consumed D. citri adults. This predator represents a potential agent for natural control of D. citri in the North of Mexico, and South of the USA, mainly through conservation strategies of beneficial insects.

Extension Model to Improve Asian Ctrus Psyllid Control in Citrus Health Management Areas (CHMAs)

Citrus health management areas (CHMAs) have been implemented throughout Florida to provide regional coordination to manage Asian citrus psyllid (ACP) and spread of HLB.&nbsp; The Gulf CHMA is going into its 5th season of cooperative action toward these goals.&nbsp; During the fourth (2011-2012) season we began providing GULF CHMA updates and interactive maps from CHRP data available on the CHMA website www.flchma.com, showing ACP levels and 'hot spots' (i.e. tap samples &gt; 21 ACP for 3 consecutive cycles) on our website, www.imok.ufl.edu.&nbsp;&nbsp; The ring color of the proportional circle map designates the cycle, and the ring size the number of A adults per 50 taps.&nbsp; The largest ring represents psyllid numbers of 21 or greater.&nbsp; The map is readable by anyone with Adobe Reader, and it allows you to click on and off different cycle layers and view data for Cycle #, Cycle Date, County Name, and ACP # thus allowing comparison between two or more sets of data simultaneously and spatially.&nbsp; This project includes development and testing of a smart phone spray app for use by growers and consultants.&nbsp; The insecticide spray data will be converted to a map layer that overlays the Gulf CHMA psyllid counts to determine which growers may need help and what chemicals appear to be failing -- a precursor to predicting ACP resistance.&nbsp; We expect to build better working relationships with the growers by offering individual support of their economic efforts, ACP management, and HLB control.

A grower question: So we are controlling the Asian Citrus Psyllid, but are we doing it well enough?

Since Huanglongbing (HLB) was first found in Florida, growers have recognized the importance of controlling the Asian citrus psyllid (ACP) that vectors the disease.&nbsp;&nbsp; ACP management programs have been developed and applied over large acreages, yet in many instances, the incidence of the disease continues to increase.&nbsp;&nbsp; When asked, the growers invariably report that they are controlling ACP and it is obvious that the control programs are reducing the level of ACP in the groves.&nbsp; However there is an outstanding question as to whether the levels of ACP are being reduced enough to limit the spread of HLB.&nbsp; In most cases, growers have not implemented ACP scouting programs so the level of infestation is based on rough grove surveys and feelings.&nbsp; Even if scouting programs are in place, there are no established data-based thresholds to trigger additional applications of pesticides resulting in a “chasing” approach where applications are made after an infestation is found.&nbsp; Southern Gardens has had an ACP and HLB scouting program in place for many years.&nbsp; By comparing the annual ACP levels to resulting HLB infection succeeding years, it may be possible to elucidate thresholds and then design ACP control programs that effectively limit the spread of HLB.&nbsp; Data will be presented for three years of ACP scouting and four years of HLB scouting in an attempt to show the level of control that must be achieved in order to limit the spread of HLB.&nbsp; The bottom line is that control thresholds are very low and the level of ACP control that must be achieved in order to limit spread HLB is much lower than most growers realize.

Affordable Essential Oils for Management of the Asian Citrus Psyllid

Plant essential oils are commonly used to manage insects; they are widely available and some are inexpensive.&nbsp; In this research we have selected five botanical oils costing less than $100 US per kilogram, to evaluate for repellency to Asian Citrus Psyllid (ACP), the insect vector of the causal pathogens of huanglongbing.&nbsp; In olfactometer assays, fir oil was repellent; clove and camphor oils were attractive; and litsea and citronella oils elicited no response from ACP females.&nbsp; In no-choice settling experiments, neither the low nor high fir oil treatment deterred ACP from settling.&nbsp; Subsequently, ACP were presented with a choice test between control plants and fir oil plants with a single dose of fir oil contained in a polyethylene vial.&nbsp; In this case, ACP disproportionately settled on control plants, avoiding fir oil baited trees completely.&nbsp; Finally, we conducted a field trial using yellow sticky traps baited with a high or low dose of clove or camphor oil deployed from seven mL polyethylene vials.&nbsp; We expected that the botanical oil baited yellow traps would catch more ACP than unbaited controls.&nbsp; There was no significant increase in trap capture over the course of our experiment in male, female, or total ACP capture.&nbsp; We hypothesize that this result may have been caused by sub-optimal release rates or the overriding visual cue elicited by yellow sticky traps. Our ongoing experiments are designed to improve the behavioral activity of release devices for these essential oils, which may have practical utility for ACP management.